Chronic fatigue syndrome (CFS) is being reported with increasing frequency in many sections of the United States as well as other parts of the world, including England and Australia. In many patients, CFS begins with an acute "flu-like" illness and is characterized by a debilitating fatigue lasting for more than 3-6 months; chronic and recurrent low-grade fever, pharyngitis, adenopathy, myalgia, arthralgia, sleep disorders and mood disorders. A common feature is multilevel brain disorder, reflected in mental changes such as loss of memory, vertigo, and disorientation, often described as "spaciness." Direct measurements of brain function using, for example, magnetic resonance imaging (MRI) have indicated abnormalities in the central nervous system. Dementia and signs of "mental clouding" have also been documented through psychoneurologic testing.
The infectious agent(s) for CFS is unknown; the agent is suspected to be viral, at least in part because many viral infections are characterized by chronic fatigue. However, post viral fatigue generally does not persist for more than a few weeks, which is contrary to the clinical picture in CFS. Conclusive evidence of an etiologic association of a particular known virus to CFS has not been presented, although high levels of antibodies to Epstein Barr virus (EBV), human herpes virus-6 (HHV-6) and the p24 core antigen of HTLV have been reported. Further, certain immunologic abnormalities described in CFS are often found in viral infections, including activation of CD8+ cells. Other immunologic abnormalities observed include decreased function of NK cells, reduced mitogenic responses of lymphocytes and B-cell subset changes.
It is of interest to determine whether there are virologic and immunologic parameters which are at least substantially specific for CFS so that they can be used as a diagnostic aid in those patients who present with symptoms including chronic fatigue. Further, definitive diagnosis of CFS is hampered by the lack of a screening test such as an immune profile or a serologic test to identify the etiologic agent. Identification of the etiologic agent to produce recombinant proteins that are safe for use in vaccines, diagnostics, and/or screening of the blood supply is greatly desired.